Effects Of High Temperature And Water Stress During Grain Filling On Starch Quality Of Waxy Maize

The study was conducted on the Experimental Farm of Agricultural College,Yangzhou University in 2016 and 2017.The temperature after pollination was control by intelligent greenhouse,and the water content was controlled by weighing method and monitored by soil moisture velocimeter.The effects of high temperature(35?)and water stress(drought or waterlogging,soil relative moisture was 55-60%and 95-100%,respectively)on grain yield and starch quality of waxy maize were studied using Suyunuo 5 and Yunuo 7 as materials.The main results were as follows:High temperature and water(drought or waterlogging)stress during grain filling reduced the grain number and decreased the grain weight,which led to the grain yield loss,and the effects of interaction of high temperature and water stress were higher than the effects of the single factor.The grain starch and soluble sugar was decreased,whereas the grain protein content and prolamin content was increased by adversity,and the influence was higher when high temperature and drought/waterlogging occurred concurrently.The microelements(S,Ca,and Cu)contents was little affected by drought and increased under the other stress conditions.The Fe,Mn,and Zn contents were all increased by the single or interaction of high temperature,drought and waterlogging.High temperature and water stress(single or interaction)decreased the flour peak viscosity,the decrease was higher under single heat than drought and waterlogging,whereas the serious decrease was presented when high temperature and waterlogging occurred synchronized.The breakdown viscosity was decreased by all the stress.The setback viscosity was little affected by waterlogging and heat/drought stress but increased by the other stresses.The pasting temperature was not affected by waterlogging and heat/waterlogging but increased by the other stresses.The flour onset,peak and conclusion temperatures were increased by all the stress except waterlogging.The gelatinization enthalpy was increased by stresses except drought,while retrogradation enthalpy and percentage were increased by all the stresses.The correlation analysis results indicated the protein content and average starch granule size was negative correlated to peak and breakdown viscosities and positively correlated to pasting temperature.The retrogradation percentage was positively correlated to average starch granule size.The starch granule size and the percentage of the large granule(diameter>15?m)were increased by high temperature,and interaction of high temperature and drought or waterlogging,while those two parameters were reduced when plants only suffered drought or waterlogging.The grain granule surface presented more gap,microvoid,and pitting when plants suffered adversity during grain development.The starch iodine binding capacity was increased by adversity.Under the stress conditions,the short-length amylopectin percentage and the ratio of short/long amylopectin length were decreased,as observed by gel permeation chromatography(GPC).The results of high performance anion exchange chromatography(HPAEC)observed that the percentage of fa(DP 6-12,part of the A-chain)was decreased and the percentage of fb3(DP>37)were increased under all the stress conditions.The crystalline structure of the starch was not changed under the stress conditions,and all the samples present typical A-type diffraction pattern,while the relative crystallinity in response to adversity was dependent on the variety and plant year.The starch peak viscosity was not affected by drought stress and reduced under the other stress conditions.The trough viscosity was increased by high temperature,drought,and heat/drought conditions,the value was not affected by waterlogging but decreased by the interaction of heat and waterlogging.The breakdown and setback viscosities were decreased,whereas pasting temperature was increased by stresses.The starch gelatinization enthalpy was generally not affected by high temperature and water stress,while onset,peak,and conclusion temperatures,retrogradation enthalpy and percentage were increased by stress.Starch peak viscosity was positively correlated to ratio of A/B chain.Breakdown viscosity positively correlated to the ratio of A/B chain and short/long chain,and negatively correlated to iodine binding capacity and ratio of 1047/1022.Pasting temperature positively correlated to ratio of 1047/1022 and average granule size,and negative correlated to the ratio of short/long chain.Retrogradation percentage was positively correlated to iodine binding capacity and negatively correlated to the ratio of short/long chain.The peak thermal decomposition temperature was observed positively correlated to the ratio of short/long chain and A/B chain.